I think bringing Boba Fett back would just make the universe feel smaller. It'd be like putting Chewy in Revenge of the Sith, it's not really bad, but it's not really good either.

Personally I'd like to see a whole new type of dangerous underworld scum in the new films. With the fall of the Empire in Jedi and the reconstruction process of the Republic these could arguably be the darkest times of all three trilogies.